There were significant differences in brain amyloid content exhibited on positron emission tomography of patients with normal and impaired cognition, suggesting PET might have a role in differential diagnosis of dementia, investigators in a multicenter study concluded. The standard uptake value ratios (SUVRs) for the tracer florbetapir F 18 declined in linear fashion from patients with probable Alzheimer's disease to those with mild cognitive impairment to a group of older normal controls. The pattern of differences in SUVR persisted in analyses of mean cortical florbetapir, proportion of patients with amyloid levels associated with Alzheimer's disease, and the proportion with any identifiable fibrillar beta-amyloid (P<1 x 10-7 for all comparisons), as reported online in Archives of Neurology.